[quote=Dooghan;271524]I would think gravity would be a bigger problem then cost. Trying to move the tube from anything then straight up and the mirror would go out of focus. I remember watch a program on TV and they where saying they would like to use mercury in the in next generation big telescopes. It would make the perfect mirror but they would have to build it on the moon because of gravity.
They have to seal it off from the operators too, the fumes of that stuff are nasty. Used to work on Mercury bath lighthouse lens bearings, dressed up like something out of chemical warfare.
Bill
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